/*
 * Test passing array (pointer) as argument.
 */
double fib[1000];

int Story_of_time(int n, double fib[])
{
	int i = 2;
	
	while (i <= n)
	{
		fib[i] = fib[i - 1] + fib[i - 2];
		i = i + 1;
	}
	return n;
}

int main()
{
	int n;
	n = get_int();
	fib[0] = 1.0;
	fib[1] = 1.0;
	Story_of_time(n, fib);
	print_double(fib[n]);
	return 0;
}